Railroad hopper cars are used to transport a wide variety of aggregate lading such as coal, gravel, crushed stone, phosphate fertilizer rock and the like. Most of the cars produced up to the present time have been made of steel and when a corrosive product is to be transported the cars have been coated with various materials to protect the steel.
Because of the increased fuel costs which have occurred in recent years, continuous efforts have been made to reduce the empty weight of railroad cars to lower fuel consumption. Considerable car weight reduction has been achieved by new car designs. However, it has been realized that to further reduce car weight the use of steel must be reduced as much as possible by use of lighter substitute materials. Presently, the most promising material is aluminum because it is light weight, available at reasonable cost and has good corrosion resistant properties.
Aluminum hopper cars, especially for carrying coal and similar aggregate materials, have been recently developed. Such cars, however, realistically require a steel center sill to carry the loads and withstand train buff and draft forces. To protect the steel center sill against corrosion, and to facilitate unloading of the cargo, the steel center sill is covered by a peaked or gabled aluminum center sill hood. The aluminum center sill hood intersects aluminum cross ridge hoods, which cover discharge door operating apparatus, and the car sloped end walls. Joining these intersections by aluminum welds was expected to provide joints of adequate strength but that was found to be an erroneous assumption because they failed in use. A need accordingly exists for an alternative system for suitably interconnecting such intersections.